Human breast carcinoma cells transfected with the gene encoding a c-myc promoter-binding protein (MBP-1) inhibits tumors in nude mice.

We have identified previously a gene from a human cervical carcinoma cell (HeLa) cDNA expression library that encodes a M(r) approximately 37,000 c-myc promoter-binding protein (MBP-1), which binds to the TATA box sequences of c-myc P2 promoter and exerts a negative regulatory function by down-regulating c-myc expression. In normal human tissues, this cloned gene showed variable expression. In this study, we have demonstrated that introduction of the MBP-1 gene into human breast carcinoma cells reduced their ability to invade through a basement membrane matrix in vitro but did not alter their growth rate. Human breast carcinoma transfected with MBP-1 cells showed a loss of anchorage-independent growth and also suppressed tumor formation in athymic nude mice. These results suggest the possible involvement of MBP-1 as a tumor suppressor gene in human breast carcinoma cells.